This invention relates to a heat exchanger for use with artificial heart and lung devices.
In the case of circulating the blood of a patient through an artificial heart and lung device in a surgical operation on his heart, the temperature of the blood generally tends to drop while it is circulated through the circuit outside the patient's body because the temperature in the operation room is lower than the body temperature thereof. In order to heat the blood to the body temperature again and return it to the patient's body, it is essential to provide a heat exchanger.
As for heat exchangers for use with artificial heart and lung devices, there have heretofore been employed two types. One type includes one length of a blood transport tube within a tubular shell, and the other type includes a spiral blood transport tube mounted within a tubular shell in which a heating medium is introduced to heat the blood. These devices are, however, disadvantageous in that since the surface area through which the blood can receive the heat from the heating medium is small, the heat exchanging efficiency obtainable thereby is low. In order to eliminate the above-mentioned disadvantage, the applicant of the present invention devised and filed a Japanese Utility Model Application No. 119,356/1947 in which a large number of elongated tubes are mounted in parallel within a tubular shell to improve the heat exchanger efficiency. This device can provide a high heat exchanging efficiency since the surface area through which the blood can receive the heat from the heating medium is large, and can be put satisfactorily into practical use. However, it has a room left to be improved, because it is not provided with means for removing air bubbles produced in the blood.
In artificial heart and lung devices, it is necessary to add some amount of oxygen to the blood passing therethrough by spraying oxygen to the blood. Therefore, the passage of the blood oversaturated with oxygen inside the heat exchanger allows the oxygen in the blood to expand by heating thereby producing oxygen bubbles. Conventional devices are disadvantageous in that since they are not provided with means for removing such air bubbles, it is absolutely necessary for a doctor to frequently remove the air bubbles to avoid complications resulting from the bubbles.